U.S. patent number 8,101,536 [Application Number 12/516,295] was granted by the patent office on 2012-01-24 for glass-free microwave dielectric ceramics and the manufacturing method thereof.
This patent grant is currently assigned to Korea Institute of Ceramic Engineering & Technology. Invention is credited to Hyo Tae Kim, Jong Hee Kim, Myung Hwa Nam.
United States Patent |
8,101,536 |
Kim , et al. |
January 24, 2012 |
Glass-free microwave dielectric ceramics and the manufacturing
method thereof
Abstract
A glass-free microwave dielectric ceramic that can be sintered
at low temperature is provided. The glass-free microwave dielectric
ceramic composition includes
(M.sub.1-x.sup.2+M'.sub.x.sup.2+)N.sup.4+B.sub.2O.sub.6 (wherein M
and M' are different each other, each being one among Ba, Ca and
Sr; N is one among Sn, Zr and Ti; and 0<x<1),
M.sup.2+(N.sub.1-y.sup.4+N'.sub.y.sup.4+)B.sub.2O.sub.6 (wherein M
is one among Ba, Ca and Sr; N and N' are different from each other,
each being one among Sn, Zr and Ti; and 0<y<l), or
(M.sub.1-x.sup.2+M'.sub.x.sup.2+)(N.sub.1-y.sup.4+)B.sub.2O.sub.6
(wherein M and M' are different from each other, each being one
among Ba, Ca and Sr; N and N' are different from each other, each
being one among Sn, Zr and Ti; 0<x<1; and 0<y<l). In
addition, the glass-free microwave dielectric ceramic composition
may further includes approximately 1 wt % to approximately 7 wt %
of a sintering aid represented by a formula,
0.12CuO+0.88Bi.sub.2O.sub.3. As such, the glass-free microwave
dielectric ceramic composition may be sintered at a low temperature
at lowest 875.degree. C.
Inventors: |
Kim; Hyo Tae (Gyeonggi-do,
KR), Kim; Jong Hee (Seoul, KR), Nam; Myung
Hwa (Seoul, KR) |
Assignee: |
Korea Institute of Ceramic
Engineering & Technology (KR)
|
Family
ID: |
39468032 |
Appl.
No.: |
12/516,295 |
Filed: |
November 22, 2007 |
PCT
Filed: |
November 22, 2007 |
PCT No.: |
PCT/KR2007/005906 |
371(c)(1),(2),(4) Date: |
December 15, 2009 |
PCT
Pub. No.: |
WO2008/066282 |
PCT
Pub. Date: |
June 05, 2008 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20100120607 A1 |
May 13, 2010 |
|
Foreign Application Priority Data
|
|
|
|
|
Nov 30, 2006 [KR] |
|
|
10-2006-0120128 |
|
Current U.S.
Class: |
501/135; 501/137;
501/136; 501/138; 501/139 |
Current CPC
Class: |
C04B
35/01 (20130101); C04B 2235/3208 (20130101); C04B
2235/656 (20130101); H05K 1/0306 (20130101); C04B
2235/767 (20130101); C04B 2235/3293 (20130101); C04B
2235/3298 (20130101); C04B 2235/3244 (20130101); C04B
2235/3281 (20130101); C04B 2235/80 (20130101); C04B
2235/3215 (20130101); C04B 2235/3232 (20130101); C04B
2235/3213 (20130101); C04B 2235/3409 (20130101) |
Current International
Class: |
C04B
35/453 (20060101); C04B 35/457 (20060101); C04B
35/465 (20060101); C04B 35/486 (20060101) |
Field of
Search: |
;501/136,137,138,139,135 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
61091528 |
|
May 1986 |
|
JP |
|
63280488 |
|
Nov 1988 |
|
JP |
|
01183448 |
|
Jul 1989 |
|
JP |
|
2000203878 |
|
Jul 2000 |
|
JP |
|
2000252106 |
|
Sep 2000 |
|
JP |
|
Other References
The International Search Report issued in connection with
PCT/KR/2007/005906 on Feb. 28, 2008. cited by other .
Nam, Myung-Hwa et al. Low-Temperature Sintering and Dielectric
Properties of BaSn(BO3)2. Journal of the Korean Ceramic Society.
Feb. 2006, vol. 43, No. 2, pp. 92-97. cited by other .
Translated Abstract for JP 2000203878, Jul. 2000. cited by other
.
Translated Abstract for JP 2000252106, Sep. 2000. cited by
other.
|
Primary Examiner: Group; Karl
Attorney, Agent or Firm: The H.T. Than Law Group
Claims
The invention claimed is:
1. A dielectric ceramic composition, comprising a composition
represented by a formula:
(M.sub.1-x.sup.2+M'.sub.x.sup.2+)N.sup.4+B.sub.2O.sub.6, wherein M
and M' are different from each other, each being one among Ba, Ca
and Sr; N is one among Sn, Zr and Ti; and 0<x<1.
2. A dielectric ceramic composition, comprising a composition
represented by a formula:
M.sup.2+(N.sub.1-y.sup.4+N'.sub.y.sup.4+)B.sub.2O.sub.6 wherein M
is one among Ba, Ca and Sr; N and N' are different from each other,
each being one among Sn, Zr and Ti; and 0<y<1.
3. A dielectric ceramic composition, comprising a composition
represented by a formula:
(M.sub.1-x.sup.2+M'.sub.x.sup.2+)(N.sub.1-y.sup.4+N'.sub.y.sup.4+)B.sub.2-
O.sub.6, wherein M and M' are different from each other, each being
one among Ba, Ca and Sr; N and N' are different from each other,
each being one among Sn, Zr and Ti; 0<x<1; and
0<y<1.
4. The dielectric ceramic composition of claim 1 further comprising
a sintering aid including CuO and Bi.sub.2O.sub.3.
5. The dielectric ceramic composition of claim 1 further comprising
a sintering aid represented by a formula:
0.12CuO+0.88Bi.sub.2O.sub.3.
6. The dielectric ceramic composition of claim 4, wherein the
content of the sintering aid in the dielectric ceramic composition
is from 1 wt % to 7 wt %.
7. The dielectric ceramic composition of claim 2, further
comprising a sintering aid including CuO and Bi.sub.2O.sub.3.
8. The dielectric ceramic composition of claim 3, further
comprising a sintering aid including CuO and Bi.sub.2O.sub.3.
9. The dielectric ceramic composition of claim 2, further
comprising a sintering aid represented by a formula:
0.12CuO+0.88Bi.sub.2O.sub.3.
10. The dielectric ceramic composition of claim 3, further
comprising a sintering aid represented by a formula:
0.12CuO+0.88Bi.sub.2O.sub.3.
11. The dielectric ceramic composition of claim 7, wherein the
content of the sintering aid in the dielectric ceramic composition
is from 1 wt % to 7 wt %.
12. The dielectric ceramic composition of claim 8, wherein the
content of the sintering aid in the dielectric ceramic composition
is from 1 wt % to 7 wt %.
Description
This application claims priority to international patent
application no. PCT/KR2007/005906 filed on Nov. 22, 2007 and to
Korean patent application no. KR 10-2006-0120128 filed on Nov. 30,
2006. The disclosures of these applications are incorporated herein
by reference in their entireties.
TECHNICAL FIELD
The present disclosure relates to a microwave dielectric ceramics
and a manufacturing method thereof, and more particularly, to a
glass-free microwave dielectric ceramics which can be sintered
together with an internal conductor and has superior microwave
dielectric characteristics, and a manufacturing method thereof.
BACKGROUND ART
Recently, as a market for mobile communication terminals, such as a
mobile phone and a personal digital assistant (PDA), and Bluetooth
products for facilitating ubiquitous communications is growing
rapidly, high-frequency devices constituting them, such as a
microwave filter, a duplexer, a resonator, and an integrated
circuit board are required to become smaller and lighter, and to be
stacked and surface-mounted.
Such high-frequency devices include dielectric ceramic materials.
The dielectric ceramics for the high-frequency devices should have
specific dielectric characteristics as follows.
First, in order to reduce the device size, the dielectric ceramics
should have a high dielectric constant, .di-elect cons..sub.r. This
is because a wavelength of the microwave in the dielectric ceramics
is decreased in inverse proportion to the square root of the
dielectric constant. However, a microwave transmission line
provided to a board of radio frequency (RF)/microwave module should
rather have a low dielectric constant so as to increase the
speed.
Second, for a highly efficient operation, the dielectric ceramics
should have a high quality factor (Q) within an operation frequency
range. In other words, the dielectric ceramics should have a low
dielectric loss, tan .delta., which is a reciprocal of the quality
factor. In general, the quality factor is evaluated based on the
product of the quality factor and a corresponding resonance
frequency, Q.times.f, or the dielectric loss, a reciprocal of the
quality factor.
Third, for an accurate operation of the operation frequency, the
dielectric ceramics should have a temperature coefficient factor
(TCF) of the resonance frequency, .tau..sub.f, close to zero.
Meanwhile, a method for stacking high-frequency devices under
development in recent times includes printing a conductive pattern
on a green sheet of dielectric ceramics, stacking the printed green
sheets, and then sintering them. This method allows lots of
elements such as an inductor, a capacitor and a resistor to be
integrated in a single module without additional lead wire.
Accordingly, the package size can be reduced significantly.
However, the method requires that an internal conductor formed of
silver (Ag) or copper (Cu) having excellent conductivity should be
sintered together with the dielectric ceramics. Accordingly, a low
temperature co-fired ceramics (LTCC) is demanded strongly. The LTCC
can be sintered at a temperature lower than approximately
950.degree. C., however, has a high quality factor and a low
resonance frequency. However, most of the recently developed LTCC
suffers from significantly deteriorated microwave dielectric
characteristics, such as insufficient densification, low dielectric
constant clue to the addition of sintering agents, lowered quality
factor, increased temperature coefficient factor of the resonance
frequency, and the like.
Furthermore, the typical LTCC is formed of ceramic materials having
a composite structure including a glass matrix and an alumina
(Al.sub.2O.sub.3) powder filler mixed thereto. However, this
typical LTCC is reported to suffer from difficulty in controlling
rheology during the ceramic slurry formation, ununiform glass
composition, ununiform dispersion, and the like. Consequently, a
glass-free (or non-glass) LTCC composition including no glass or
minimum amount of glass is attracting considerable interests.
DISCLOSURE
Technical Problem
Accordingly, the present disclosure provides a glass-free microwave
dielectric ceramics having superior microwave dielectric
characteristics, and a manufacturing method thereof.
The present disclosure also provides a low temperature co-fired
microwave dielectric ceramics that can be sintered at low
temperature by adding a low temperature sintering agent to the
glass-free microwave dielectric ceramics, and a manufacturing
method thereof.
Technical Solution
Embodiments provide a microwave dielectric ceramics includes
M.sup.2+N.sup.4+B.sub.2O.sub.6 component, where M may be
substituted for by two different divalent metals and/or N may be
substituted for by two different tetravalent metals.
Advantageous Effects
A microwave dielectric ceramic in accordance with an exemplary
embodiment includes M.sup.2+N.sup.4+B.sub.2O.sub.6 composition.
Here, M may be replaced by two divalent metals different from each
other and/or N may be replaced by two tetravalent metals different
from each other. As such, the microwave dielectric ceramic can have
superior microwave dielectric characteristics without a glass
matrix, and thus can be advantageously applied to a high-frequency
device.
In addition, by adding Bi.sub.2O.sub.3--CuO based sintering agent
to the microwave dielectric ceramic composition, the microwave
dielectric ceramic can be sintered at low temperature without
deterioration of dielectric characteristics. Accordingly, the
microwave dielectric ceramic can be advantageously applied to a low
temperature co-firing ceramic device, which has superior microwave
dielectric characteristics.
DESCRIPTION OF DRAWINGS
FIG. 1 is a graph illustrating microwave dielectric characteristics
of BaZr(MO.sub.3).sub.2 ceramic in accordance with an exemplary
embodiment.
FIG. 2 is a scanning electron microscope (SEM) image of the
BaZr(MO.sub.3).sub.2 ceramic of FIG. 1.
FIG. 3 is a SEM image of Ba(Zr.sub.1-xTi.sub.x)B.sub.2O.sub.6
ceramic sintered for 2 hours at 1,050.degree. C. in accordance with
another exemplary embodiment.
FIG. 4 is a SEM image of BaZr(BO.sub.3).sub.2 ceramic added with 5
wt % of 0.88Bi.sub.2O.sub.3-0.12CuO as a sintering agent, and
sintered for 2 hours at 900.degree. C. in accordance with further
another exemplary embodiment.
BEST MODE
In accordance with an exemplary embodiment, a glass-free microwave
dielectric ceramic composition includes a composition represented
by a formula, M.sup.2+N.sup.4+B.sub.2O.sub.6, wherein M is one
element of Ba, Ca and Sr, and N is one element of Sn, Zr and
Ti.
The M may be replaced by two elements of Ba, Ca and Sr different
from each other, to form a composition represented by a formula,
(M.sub.1-x.sup.2+M'.sub.x.sup.2+)N.sup.4+B.sub.2O.sub.6 (wherein M
and M' are different from each other, each being one among Ba, Ca
and Sr; N is one among Sn, Zr and Ti; and 0<x<1). The N may
also be replaced by two elements of Sn, Zr and Ti different from
each other, to form a composition represented by a formula,
M.sup.2+(N.sub.1-y.sup.4+N'.sub.y.sup.4+)B.sub.2O.sub.6 (wherein M
is one among Ba, Ca and Sr; N and N' are different from each other,
each being one among Sn, Zr and Ti; and 0<y<1). Furthermore,
it is also possible that the M is replaced by two elements of Ba,
Ca and Sr different from each other, and the N is replaced by two
elements of Sn, Zr and Ti different from each other, to form a
composition represented by a formula,
M.sub.1-x.sup.2+M'.sub.x.sup.2+)(N.sub.1-y.sup.4+N'.sub.y.sup.4+)B.sub.2O-
.sub.6 (wherein M and M' are different from each other, each being
one among Ba, Ca and Sr; N and N' are different each other, each
being one among Sn, Zr and Ti; 0<x<1; and 0<y<1).
In addition, the glass-free microwave dielectric ceramic
composition may further includes a sintering agent represented by a
formula, 0.12CuO+0.88Bi.sub.2O.sub.3. The concentration of the
sintering aid in the dielectric ceramic composition may be from 1
wt % to 7 wt %.
In accordance with another exemplary embodiment, a method for
manufacturing a glass-free microwave dielectric ceramic material
includes: mixing and pulverizing one of the above described
dielectric ceramic composition; drying and calcinating the mixed
and pulverized dielectric ceramic composition; mixing and
pulverizing the dried and calcinated dielectric ceramic composition
with a sintering agent represented by a formula,
0.12CuO+0.88Bi.sub.2O.sub.3, to obtain a sample; drying the sample;
molding the dried sample; and sintering the molded sample. The
sintering agent may be added in the range of from 1 wt % to 7 wt %.
The sintering of the molded sample may be performed at from
875.degree. C. to 1,000.degree. C. As such, the glass-free
microwave dielectric ceramic material can be sintered at low
temperature without significant deterioration of microwave
dielectric characteristics.
MODE FOR INVENTION
A microwave dielectric ceramic in accordance with an exemplary
embodiment has a ceramic composition represented by the formula 1:
M.sup.2+N.sup.4+B.sub.2O.sub.6 (1), where M is a divalent metal
element such as Ba, Ca, Sr, and the like, and N is a tetravalent
metal element such as Sn, Zr, Ti, and the like. The inventors found
that the microwave dielectric ceramic has a dolomite structure and
an anisotropic thermal expansion characteristic.
Also, the formula 1 may be modified by replacing the metal element
M or N by two metal elements different from each other. That is,
the formula 1 may be modified in such a manner that the metal
element M is replaced by two divalent metal elements different from
each other, and/or the metal element N is replaced by two
tetravalent metal elements different from each other. In this case,
the formula 1 of the microwave dielectric ceramic may be modified
into one of the following formulas:
(M.sub.1-x.sup.2+M'.sub.x.sup.2+)N.sup.4+B.sub.2O.sub.6 (2),
M.sup.2+(N.sub.1-y.sup.4+N'.sub.y.sup.4+)B.sub.2O.sub.6 (3),
(M.sub.1-x.sup.2+M'.sub.x.sup.2+)(N.sub.1-y.sup.4+N'.sub.y.sup.4+)B.sub.2-
O.sub.6 (4), where 0<x<1 and 0<y<1. The M and M' may be
any divalent metal elements, such as Ba, Ca, Sr, and the like,
which are different from each other. The N and N' may be any
tetravalent metal elements, such as Sn, Zr, Ti, and the like, which
are different from each other.
The inventors found that sintering temperatures of the microwave
dielectric ceramics of formulas 1 to 4 are higher than
approximately 1,100.degree. C. Such a high sintering temperature
makes the ceramics difficult to be applied to LTCC. Therefore,
according to the other desirable embodiment of the present
invention, in order to lower the sintering temperature, a sintering
agent including CuO and Bi.sub.2O.sub.3 for a low temperature
sintering is added to the composition of the microwave dielectric
ceramics having the formulas 1 to 4. The sintering agent can be
represented by the following formula: .alpha.wt
%(0.12CuO+0.88Bi.sub.2O.sub.3) (5) where 1<.alpha.<7.
In summary, the microwave dielectric ceramics of the formulas 1 to
4 are difficult to be used for the LTCC because they have sintering
temperatures higher than approximately 1,100.degree. C. However, as
a sintering agent including CuO and Bi.sub.2O.sub.3 having a
eutectic point of approximately 600.+-.20.degree. C. is added to
the microwave dielectric ceramics, the sintering temperature can be
lowered preferably to between 875.degree. C. and 1,000.degree. C.,
more preferably to between 875.degree. C. and 925.degree. C.,
further more preferably to 875.degree. C. During the sintering
process, the CuO and Bi.sub.2O.sub.3 form a liquid phase in an
internal interface of the ceramic to accelerate densification of
the ceramic. Consequently, the microwave dielectric ceramic can be
sintered at a low temperature with superior microwave dielectric
characteristics.
Hereinafter, specific embodiments will be described in detail with
reference to the accompanying drawings. The invention may, however,
be embodied in many different forms and should not be construed as
being limited to the embodiments set forth herein; rather, these
embodiments are provided so that this disclosure will be thorough
and complete, and will fully convey the concept of the invention to
those skilled in the art.
EXAMPLES 1 to 5
In these examples, BaZr(BO.sub.3).sub.2 ceramics consisting
essentially of the composition of the formula 1 were prepared and
sintered at various sintering temperatures, and microwave
dielectric characteristics thereof were measured.
In specific, reagents BaCO.sub.3, ZrO.sub.2, and B.sub.2O.sub.3 or
H.sub.3BO.sub.3 were weighed to form the composition of
BaZr(BO.sub.3).sub.2. The weighed reagents were mixed and
pulverized with zirconia balls for 24 hours using deionized water
as a dispersion solvent. The mixed and pulverized sample was dried,
and then calcinated for 4 hours at between 900.degree. C. and
1,150.degree. C. to synthesize a solid solution of a dolomite
structure (hexagonal symmetry). The synthesized powder was
pulverized again for 24 hours with a wet ball mill to form a fine
powder having an average particle diameter of approximately 1
.mu.m. The fine powder was added with 2 wt % of polyvinyl alcohol
(PVA) binder aqueous solution, and pressed into a cylinder shape of
10 mm diameter and 5 mm to 6 mm thickness, at 1 ton/cm.sup.2. The
sample of a cylinder shape was heat-treated for 1 hour at
400.degree. C. to remove a binder, and then sintered for 2 hours at
a temperature between 1,100.degree. C. and 1,300.degree. C. Both
edges of the sintered sample were ground with SiC abrasive paper.
Then, dielectric constant (.di-elect cons..sub.r) at 1 MHz,
dielectric loss (tan .delta.), and temperature coefficient of
capacitance (TCC) was measured by an impedance analyzer (4294A,
Agilent Technologies Inc., USA). Here, the TCC was measured at a
temperature range from -25.degree. C. to 125.degree. C. Also,
dielectric characteristics in a microwave region were measured by a
network analyzer (8720ES, Agilent Technologies Inc., USA) with a
post resonator method and a cavity resonator method. Here, the
temperature coefficient of resonant frequency (.tau..sub.f) was
measured at a temperature range from 25.degree. C. to 80.degree.
C.
The microwave dielectric characteristics of the samples according
to the sintering temperature ranging from 1,100.degree. C. to
1,300.degree. C. are shown in Table 1 and FIG. 1.
TABLE-US-00001 TABLE 1 Temperature Sintering Dielectric Quality
coefficient temperature Frequency constant factor (.tau..sub.f:
ppm/ Example (.degree. C.) (GHz) (.epsilon..sub.r) (Q) .degree. C.)
1 1,100 15.3276 11.16 902 -0.3 2 1,150 15.0991 10.71 1,003 -6.1 3
1,200 7.4247 11.25 2,073 -13.7 4 1,250 13.0001 11.99 587 -2.1 5
1,300 13.0600 11.82 652 -1.4
Referring to Table 1 and FIG. 1, the BaZr(BO.sub.3).sub.2 ceramic
sintered at 1,100.degree. C. shows a quality factor of
approximately 900 at a frequency of 15 GHz and a dielectric
constant of approximately 11. Example 3 sintered for 2 hours at
1,200.degree. C. shows the highest quality factor of 2,073 among
the above-listed examples. FIG. 2 shows a SEM image of Example
3.
On the contrary, Examples 4 and 5 shows significantly reduced
quality factors as the sintering temperature increases above
1,250.degree. C. This is probably because BaZr(BO.sub.3).sub.2
phase is decomposed to generate BaZrO.sub.3 phase.
EXAMPLES 6 to 9
In these examples, CaZr(BO.sub.3).sub.2 ceramics consisting
essentially of the composition of the formula 1 were prepared and
microwave dielectric characteristics thereof according to
respective sintering temperatures were measured. CaCO.sub.3,
ZrO.sub.2, and B.sub.2O.sub.3 or H.sub.3BO.sub.3 were used as
starting materials. Sample preparation and measurement procedures
were essentially identical to those described in Examples 1 to 5
except the sintering temperature. In these examples, samples were
sintered for 2 hours at a temperature from 1,000.degree. C. to
1,150.degree. C.
The microwave dielectric characteristics of the
CaZr(BO.sub.3).sub.2 ceramics prepared and measured according to
these examples are shown in Table 2.
TABLE-US-00002 TABLE 2 Temperature Sintering Dielectric Quality
coefficient temperature Frequency constant factor (.tau..sub.f:
ppm/ Example (.degree. C.) (GHz) (.epsilon..sub.r) (Q) .degree. C.)
6 1,000 16.5118 -- 1,555 -- 7 1,050 16.3868 -- 1,873 -- 8 1,100
16.1439 7.4 1,914 -9.6 9 1,150 16.2759 -- 1,761 --
EXAMPLES 10 to 13
In these examples, SrZr(BO.sub.3).sub.2 ceramics consisting
essentially of the composition of the formula 1 were prepared and
microwave dielectric characteristics thereof according to
respective sintering temperatures were measured. SrCO.sub.3,
ZrO.sub.2, and B.sub.2O.sub.3 or H.sub.3BO.sub.3 were used as
starting materials. Sample preparation and measurement procedures
were essentially identical to those described in Examples 6 to
9.
The microwave dielectric characteristics of the
SrZr(BO.sub.3).sub.2 ceramics prepared and measured according to
these examples are shown in Table 3.
TABLE-US-00003 TABLE 3 Temperature Sintering Dielectric Quality
coefficient temperature Frequency constant factor (.tau..sub.f:
ppm/ Example (.degree. C.) (GHz) (.epsilon..sub.r) (Q) .degree. C.)
10 1,000 16.5607 -- 1,002 -- 11 1,050 16.3841 -- 1,275 -- 12 1,100
16.1126 7.0 2,074 -9.1 13 1,150 15.8069 -- 933 --
EXAMPLES 14 to 17
In these examples, SrSn(BO.sub.3).sub.2 ceramics consisting
essentially of the composition of the formula 1 were manufactured
and microwave dielectric characteristics thereof according to
respective sintering temperatures were measured. SrCO.sub.3,
SnO.sub.2, and B.sub.2O.sub.3 or H.sub.3BO.sub.3 were used as
starting materials. Sample preparation and measurement procedures
were essentially identical to those described in Examples 6 to
9.
The microwave dielectric characteristics of the
SrSn(BO.sub.3).sub.2 ceramics prepared and measured according to
these examples are shown in Table 4.
TABLE-US-00004 TABLE 4 Temperature Sintering Dielectric Quality
coefficient temperature Frequency constant factor (.tau..sub.f:
ppm/ Example (.degree. C.) (GHz) (.epsilon..sub.r) (Q) .degree. C.)
14 1,000 17.2340 -- 665 -- 15 1,050 16.6507 -- 1,030 -- 16 1,100
16.1751 7.1 1,150 -3.9 17 1,150 15.8567 -- 960 --
EXAMPLES 18 to 21
In these examples, CaSn(BO.sub.3).sub.2 ceramics consisting
essentially of the composition of the formula 1 were prepared and
microwave dielectric characteristics thereof according to
respective sintering temperatures were measured. CaCO.sub.3,
SnO.sub.2, and B.sub.2O.sub.3 or H.sub.3BO.sub.3 were used as
starting materials. Sample preparation and measurement procedures
were essentially identical to those described in Examples 6 to
9.
The microwave dielectric characteristics of the
CaSn(BO.sub.3).sub.2 ceramics prepared and measured according to
these examples are shown in Table 5.
TABLE-US-00005 TABLE 5 Temperature Sintering Dielectric Quality
coefficient temperature Frequency constant factor (.tau..sub.f:
ppm/ Example (.degree. C.) (GHz) (.epsilon..sub.r) (Q) .degree. C.)
18 1,000 17.7197 -- 480 -- 19 1,050 17.4157 -- 567 -- 20 1,100
17.2590 5.6 790 -4.6 21 1,150 16.9775 -- 640 --
EXAMPLES 22 to 29
In these examples, Ba(Zr.sub.1-xTi.sub.x)B.sub.2O.sub.6 (where
0<x<1) ceramics consisting essentially of the composition of
the formula 3 were prepared and microwave dielectric
characteristics thereof according to respective sintering
temperatures were measured. BaCO.sub.3, ZrO.sub.2, TiO.sub.2, and
B.sub.2O.sub.3 or H.sub.3BO.sub.3 were used as starting materials.
Sample preparation and measurement procedures were essentially
identical to those described in Examples 6 to 9.
The microwave dielectric characteristics of the
Ba(Zr,Ti)B.sub.2O.sub.6 ceramics according to respective mole
fractions of Zr/Ti and respective sintering temperatures are shown
in Table 6. A SEM image of Example 22 sintered for 2 hours at
1,050.degree. C. is shown in FIG. 3.
TABLE-US-00006 TABLE 6 Com- Sintering Di- Temperature Ex- posi-
temper- electric Quality coefficient am- tion ature Frequency
constant factor (.tau..sub.f: ppm/ ple (Zr/Ti) (.degree. C.) (GHz)
(.epsilon..sub.r) (Q) .degree. C.) 22 1/1 1,050 11.9261 12.82 2,250
-31 23 1/1 1,100 12.1784 12.00 690 -23 24 1/1 1,150 12.4252 11.28
366 -46 25 1/3 1,075 7.0213 12.14 978 -- 26 3/1 1,100 7.2338 12.06
1,676 --
In addition, low frequency dielectric characteristics of Examples
22 to 24 of Ba(Zr.sub.1/2Ti.sub.1/2)B.sub.2O.sub.6 ceramics
sintered at 1,050.degree. C., 1,100.degree. C. and 1,150.degree.
C., respectively, were measured. These are shown in Table 7, as
Examples 27 to 29.
TABLE-US-00007 TABLE 7 Di- Di- Temperature Ex- Sintering electric
electric cefficient am- temperature Frequency constant loss
(.tau..sub.f: ppm/ ple (.degree. C.) (MHz) (.epsilon..sub.r) (tan
.delta.) .degree. C.) 27 1,050 1 12.66 1.8 .times. 10.sup.-4 -- 28
1,100 1 12.05 8 .times. 10.sup.-4 -- 29 1,150 1 11.96 13.3 .times.
10.sup.-4 --
EXAMPLES 30 to 33
In these examples, Ba(Sn.sub.1-xZr.sub.x)B.sub.2O.sub.6 (where
0<x<1) ceramics consisting essentially of the composition of
the formula 3 were prepared and microwave dielectric
characteristics thereof according to respective sintering
temperatures were measured. BaCO.sub.3, SnO.sub.2, ZrO.sub.2, and
B.sub.2O.sub.3 or H.sub.3BO.sub.3 were used as starting materials.
Sample preparation and measurement procedures were essentially
identical to those described in Examples 6 to 9.
The microwave dielectric characteristics of the
Ba(Sn,Zr)B.sub.2O.sub.6 ceramics according to respective mole
fractions of Sn/Zr and respective sintering temperatures are shown
in Table 8.
TABLE-US-00008 TABLE 8 Com- Sintering Di- Temperature Ex- posi-
temper- electric Quality coefficient am- tion ature Frequency
constant factor (.tau..sub.f: ppm/ ple (Sn/Zr) (.degree. C.) (GHz)
(.epsilon..sub.r) (Q) .degree. C.) 30 1/3 1,100 8.1937 9.33 173 --
31 1/1 1,100 13.9786 9.74 1,072 -- 32 1/1 1,150 13.7750 10.24 1,215
-- 33 3/1 1,100 8.2366 9.48 1,094 --
EXAMPLES 34 to 37
In these examples, a low temperature sintering agent including CuO
and Bi.sub.2O.sub.3 was added to BaZr(BO.sub.3).sub.2 ceramics of
Examples 1 to 5 in order to manufacture ceramic materials that can
be sintered at a low temperature below 1,000.degree. C.
In specific, reagents CuO and Bi.sub.2O.sub.3 were weighed to form
a sintering aid having the composition of formula 5. Then, the
BaZr(BO.sub.3).sub.2 powders calcinated and synthesized as
described in Examples 1 to 5 were added with from 1 wt % to 7 wt %
of the sintering aids having the composition of
0.12CuO+0.88Bi.sub.2O.sub.3. Thereafter, sample preparation and
measurement procedures are performed, which are identical to those
of Examples 1 to 5 after the calcination. However, the sintering
conditions were not identical to those of Examples 1 to 5. Instead,
the sintering was performed for 2 hours at a temperature from
875.degree. C. to 925.degree. C. Table 9 shows microwave dielectric
characteristics of the BaZr(BO.sub.3).sub.2 ceramics added with 5
wt % of the sintering aids having the composition of
0.12CuO+0.88Bi.sub.2O.sub.3. FIG. 4 shows a SEM image thereof when
sintering was performed for 2 hours at 900.degree. C.
TABLE-US-00009 TABLE 9 Dielectric loss (tan .delta.) Sintering
Dielectric or Temperature temperature constant Quality coefficient
Measurement Example Frequency (.degree. C.) (.epsilon..sub.r)
factor (Q) (ppm/.degree. C.) method 34 1 MHz 875 11.35 3 .times.
10.sup.-5 -- Impedance (tan .delta.) analyzer 35 1 MHz 900 11.50 7
.times. 10.sup.-5 -- (tan .delta.) 36 1 MHz 925 11.51 1 .times.
10.sup.-5 -- (tan .delta.) 37 16 GHz 900 11.80 880 +1.1 Network (Q)
analyzer
Referring to Table 9 and FIG. 4, the BaZr(BO.sub.3).sub.2 ceramic
that is added with 5 wt % of the sintering agent having the
composition of 0.12CuO+0.88Bi.sub.2O.sub.3 and sintered for 2 hours
at 900.degree. C. shows a dielectric constant of 11.8, a quality
factor of 880, and a temperature coefficient of approximately 1
ppm/.degree. C. Accordingly, the ceramic shows superior microwave
dielectric characteristics although the sintering temperature is
lowered to 900.degree. C.
EXAMPLES 38 to 43
In these examples, BaSnB.sub.2O.sub.6, CaZrB.sub.2O.sub.6,
SrZrB.sub.2O.sub.6, BaZrB.sub.2O.sub.6, CaSnB.sub.2O.sub.6, and
SrSnB.sub.2O.sub.6 ceramics consisting essentially of the
composition of the formula 1 were prepared and microwave dielectric
characteristics thereof according to respective sintering
temperatures were measured. Sample preparation and measurement
procedures were essentially identical to those described in
Examples 1 to 5 except the sintering temperature. The sintering
temperature was fixed to 1,100.degree. C.
In addition, BaSnB.sub.2O.sub.6, CaZrB.sub.2O.sub.6,
SrZrB.sub.2O.sub.6, BaZrB.sub.2O.sub.6, CaSnB.sub.2O.sub.6, and
SrSnB.sub.2O.sub.6 ceramic powders calcinated and synthesized as
described in Examples 1 to 5 were prepared. Then, the ceramic
powders were added with 5% of sintering agents having the
composition of 0.12CuO+0.88Bi.sub.2O.sub.3, and sintered at
900.degree. C., respectively. Other procedures were essentially
identical to those described in Examples 1 to 5.
The microwave dielectric characteristics of the samples prepared
and measured as described above are shown and compared in Table 10.
In Table 10, BC refers to the sintering agent having the
composition of 0.12CuO+0.88Bi.sub.2O.sub.6.
TABLE-US-00010 TABLE 10 Microwave dielectric characteristics
Quality factor (Q) (Frequency: 16 GHz) Di- 5 wt % Temperature Ex-
electric Without BC BC added coefficient am- constant (sintering
(sintering (.tau..sub.f: ppm/ ple Composition (.epsilon..sub.r) at
1,100.degree. C.) at 900.degree. C.) .degree. C.) 38
BaSnB.sub.2O.sub.6 9.8 850 350 -45 39 CaZrB.sub.2O.sub.6 7.4 1,910
1,880 -9.6 40 SrZrB.sub.2O.sub.6 7.0 2,070 1,390 -9.1 41
BaZrB.sub.2O.sub.6 11.6 1,200 902 -0.3 42 CaSnB.sub.2O.sub.6 5.6
790 1,560 -4.6 43 SrSnB.sub.2O.sub.6 7.1 1,150 1,310 -3.9
EXAMPLES 44 to 46
In these examples, (Ba.sub.1-xCa.sub.x)ZrB.sub.2O.sub.6 (where
0<x<1) ceramics consisting essentially of the composition of
the formula 2 were prepared and microwave dielectric
characteristics thereof were measured. BaCO.sub.3, CaCO.sub.3,
ZrO.sub.2, and B.sub.2O.sub.3 or H.sub.3BO.sub.3 were used as
starting materials. Sample preparation and measurement procedures
were essentially identical to those described in Examples 6 to
9.
The microwave dielectric characteristics of the
(Ba.sub.1-xCa.sub.x)ZrB.sub.2O.sub.6 ceramics according to
respective mole fractions of Ba/Ca and respective sintering
temperatures are shown in Table 11.
TABLE-US-00011 TABLE 11 Di- Temper- Ex- Compo- Sintering electric
Quality ature am- sition temperature constant factor coefficient
ple (Ba/Ca) Frequency (.degree. C.) (.epsilon..sub.r) (Q)
(ppm/.degree. C.) 44 1/1 100 MHz 1,075 11.59 1960 -- 45 1/3 100 MHz
1,075 13.29 1738 -- 46 3/1 100 MHz 1,075 10.17 1670 --
EXAMPLES 47
In this example,
(Ba.sub.1-xCa.sub.x)(Zr.sub.1-yTi.sub.y)B.sub.2O.sub.6 (where
0<x<1, 0<y<1) ceramic consisting essentially of the
composition of the formula 4 was manufactured and microwave
dielectric characteristics thereof were measured. BaCO.sub.3,
CaCO.sub.3, ZrO.sub.2, TiO.sub.2, and B.sub.2O.sub.3 or
H.sub.3BO.sub.3 were used as starting materials. Sample preparation
and measurement procedures were essentially identical to those
described in Examples 6 to 9.
The microwave dielectric characteristics of the
(Ba.sub.1-xCa.sub.x)(Zr.sub.1-yTi.sub.y)B.sub.2O.sub.6 ceramics
according to mole fractions of Ba/Ca and Zr/Ti and a sintering
temperature are shown in Table 12.
TABLE-US-00012 TABLE 12 Compo- sition Di- Temper- Ex- (Ba/Ca
Sintering electric Quality ature am- and temperature constant
factor coefficient ple Zr/Ti) Frequency (.degree. C.)
(.epsilon..sub.r) (Q) (ppm/.degree. C.) 47 1/1 100 MHz 1,000 13.17
130 --
EXAMPLES 48 to 50
In these examples, (Ba.sub.1-xCa.sub.x)ZrB.sub.2O.sub.6,
Ba(Zr.sub.1-xTi.sub.x)B.sub.2O.sub.6, and
(Ba.sub.1-xCa.sub.x)(Zr.sub.1-yTi.sub.y)B.sub.2O.sub.6 (where
0<x<1, 0<y<1) ceramics consisting essentially of the
compositions of the formulas 2 to 4, respectively, were prepared.
Then, the ceramics were added with 3 wt % of the sintering agents
having the composition of 0.12CuO+0.88Bi.sub.2O.sub.3, and sintered
at a temperature from 900.degree. C. to 925.degree. C. The
microwave dielectric characteristics of the samples prepared and
measured as described above are shown in Table 13.
TABLE-US-00013 TABLE 13 Sintering Dielectric Quality Temperature
temperature constant factor coefficient Example Composition
Frequency (.degree. C.) (.epsilon..sub.r) (Q) (ppm/.degree. C.) 48
(Ba.sub.1/2Ca.sub.1/2)ZrB.sub.2O.sub.6 + 100 MHz 925 14.09 1570 --
3 wt % (0.88Bi.sub.2O.sub.3 + 0.12CuO) 49
Ba(Zr.sub.1/2Ti.sub.1/2)B.sub.2O.sub.6 + 100 MHz 925 15.82 320 -- 3
wt % (0.88Bi.sub.2O.sub.3 + 0.12CuO) 50
(Ba.sub.1/2Ca.sub.1/2)(Zr.sub.1/2Ti.sub.1/2) 100 MHz 925 17.24 210
-- B.sub.2O.sub.6 + 3 wt % (0.88Bi.sub.2O.sub.3 + 0.12CuO)
As described above, the ceramics consisting essentially of the
compositions of the formulas 1 to 4 and added with the
Bi.sub.2O.sub.3--CuO based sintering agent can be sintered at a low
temperature ranging from 900.degree. C. to 925.degree. C. without
significant deterioration of dielectric characteristics. As such,
the ceramics in accordance with the exemplary embodiments of the
present invention can be used as an excellent material for a
capacitor, a microwave LTCC device and a substrate including silver
or copper as an internal electrode.
It will be obvious to those skilled in the art that the sintering
temperature for optimum microwave dielectric characteristics may be
varied slightly, within an acceptable error range, according to
characteristics of a powder, such as average particle size,
distribution and specific surface, purity of a starting material,
impurity content, and sintering condition.
Although the glass-free microwave dielectric ceramics and
manufacturing method thereof have been described with reference to
the specific embodiments, they are not limited thereto. Therefore,
it will be readily understood by those skilled in the art that
various modifications and changes can be made thereto without
departing from the spirit and scope of the present invention
defined by the appended claims.
* * * * *